Add some docs for the privacy notice templates #14233 (#14562)

Co-authored-by: Jan Brasna <1784648+janbrasna@users.noreply.github.com>

docs/index.rst

@@ -32,6 +32,7 @@ Contents
    newsletters
    contentful
    sitemap
+   legal-docs
    content-cards
    banners
    uitour

docs/legal-docs.rst

@@ -0,0 +1,99 @@
+.. This Source Code Form is subject to the terms of the Mozilla Public
+.. License, v. 2.0. If a copy of the MPL was not distributed with this
+.. file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+.. _legaldocs:
+
+==========
+Legal Docs
+==========
+
+Privacy notices and their applicable translations are markdown files managed by the legal
+team in the `legal-docs`_ repository.
+
+When the markdown files are imported into bedrock they are parsed using the default python
+markdown library and `BeautifulSoup`_. BeautifulSoup allows content selection and manipulation
+using `CSS selectors`_.
+
+For example the code:
+
+.. code-block:: jinja
+
+    {{ doc.select('body > section > [datetime] ~ p')|join|safe }}
+
+
+means something like:
+
+From the document, find the ``body`` element, then find the ``section`` element that is its direct descendant,
+then look for a direct descendant with a ``datetime`` attribute, select all ``p`` that are its siblings. Join
+that array of data, and then print it without filtering it for unsafe characters.
+
+If you would like to see the structure of the html you're working with, you can print it all to the page
+with ``{{ doc.select('body') }}``.
+
+
+Templates
+*********
+
+There are three templates:
+
+- base-notice
+- base-notice-headings
+- base-notice-paragraphs
+
+base-notice
+-----------
+
+This is a basic template that will extract a lead-in section and add the appropriate classes to style lists. It will
+print the rest of the privacy notice un-altered.
+
+
+base-notice-headings
+--------------------
+
+This template is preferred for longer privacy notices. It collapses content under h3 headings.
+
+The `V1.2 subscription services`_ notice is a good example of this template. It prefers content formatted like:
+
+.. code-block:: markdown
+
+    # Start the document with an h1, it will be used for the page title and first heading
+
+    Version 1.2, Effective February 5, 2024
+    {: datetime="2024-02-05" }
+
+    ## The first heading will be the heading in the lead-in section
+
+    Paragraphs after the first heading but before later headings will be displayed as part of the lead-in section.
+
+    A line will appear under the last paragraph of the lead-in.
+
+    ## This will be displayed as an h2 heading and the sibling elements will not be collapsed until an h3 is encountered
+
+    This paragraph will be visible
+
+    ### This will be displayed as an h3 heading and will serve as a toggle for all its siblings until the next h3 {: provide-an-id }
+
+    * This will be a bulleted list that is collapsed under the h3 heading
+
+    This will be a paragraph that is collapsed under the h3 heading
+
+    ### Footnote {: footnote }
+
+    If a section contains a heading with an ID of `footnote` the section will be extracted and output as the last thing on the page.
+
+    None of the elements in this section will be collapsed.
+
+
+base-notice-paragraphs
+----------------------
+
+This is an older style template that we would like to phase out in favour of the heading template. It assumes the notice will be formatted
+in a series of sections each with an introductory paragraph and then bulleted lists of further information.
+When the notice is rendered, the bulleted lists are collapsed behind a "learn more" button.
+
+
+.. _legal-docs: https://github.com/mozilla/legal-docs
+.. _Beautifulsoup: https://beautiful-soup-4.readthedocs.io/en/latest/
+.. _CSS selectors: https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_selectors
+.. _V1.2 subscription services: https://github.com/mozilla/legal-docs/blob/21c1e31ea5092565d7e3eff8aecd2612395e8497/en/subscription_services_privacy_notice.md